Investigating Ultra-Low Energy Ionization Yield from Nuclear Recoils in Semiconductor Detectors via Molecular Dynamics Simulations

TL;DR

This paper introduces a molecular dynamics simulation approach to accurately determine ionization yields from nuclear recoils in semiconductor detectors, improving understanding of low-energy interactions relevant to dark matter and neutrino detection.

Contribution

The study presents a novel, non-parameterized simulation method that explicitly incorporates crystal effects, surpassing traditional models and extending the reliability of ionization yield predictions across energy regimes.

Findings

Achieved best agreement with experimental silicon data at single EHP energy levels.

Revealed fundamental ionization yield distributions beyond single-value models.

Extended dark matter detection limits to 0.29 GeV/c^2 with distributional yields.

Abstract

Nuclear recoil ionization yield constitutes a critical uncertainty source in low-energy detection for dark matter (DM) and coherent elastic neutrino-nucleus scattering (CE$\nu$NS) experiments. We present a novel methodology employing molecular dynamics simulations to assess ionization yields in crystalline semiconductor detectors. This non-parameterized approach resolving inherent limitations of traditional Lindhard model through explicit incorporation of crystal condensed matter effects, facilitating a seamless reliability from high-energy ($E>10$\,keV) to electron-hole pair (EHP) regimes. Our model achieves the best agreement with experimental data in silicon to date, especially at the minimal energy level of a single EHP. Meticulously consideration of ion transport mechanisms reveals fundamental ionization yield distributions, superseding conventional single-value models. The distributional paradigm extends the DM-nucleon elastic scattering exclusion limit to 0.29\,GeV/$c^2$ under single-EHP sensitivity. We further report advancements in modeling quantum effects and channeling phenomena affecting ionization yields in high-purity germanium detectors.